Thread-milling machine



,July 15 1924.

- 1,501,252 G. T. TRUNDLE, JR

THREAD MILL'ING MACHINE Filed July l, 1,920 13 Sheets-Sheet 1 G. T. TRUNDLE, JRl

THREAD MILLING MACHINE 13 Sheets-Shee't 2 Filed Julky j. 1920 "July 15, 1924. y

A G. T. TRUNDLE. JR

THREAD MILLING MACHINE 13 Sheets-Sheet 5 Fil'ed July l, 1920 July 1s, 1924. y

G. T. TRUNDLE, JR

4 THREAD `MILLING MACHINE Filed lJuly 1,

1920 13 Sheets-Sheet 5' July 15, 1924. 1,501,252

G. T. TRUNDLE, JR

THREAD MILLING MACHINE Filed July l. 1920 13 Shee'S-Sl'leel 6 Zvenr July 15, 1924.

G. T. TRUNDLE, JR

THREAD MILLING MACHINE Filed July 3. 1920 13 Sheets-Sheet '7 July-15 1924. G. T. TRUNDLE. JR

THREAD MILLING MACHINE Filed July l, 1920 1'3 Sheets-Sheet 8 256 v Il! L 255 254 253 July 1.5, 1924. 1,501,252

T. TRUNDLE, JR

THREAD MILLLJNG MACHINE Filed July 1, 1920 13 Sheets-Sheet 1o 164I if) l 166 1.66 W 177 wf( l ik! l /O/ Q l//// July 15 1924.

G. T. TRUNDLE, JR

THREAD MILLING MACHINE 13 Sheets-Sheet ll Filed July 1. i920 July 15, 1924.

G. T. TRUNDLE', .1R

THREAD MILLING MACHINE .Zal

July 15, 1924.

G. T. TRUNDLE. JR

THREAD MILLING MACHINE Filed July 1. '1920 13 sheets-sheet 1s Patente-d .luly 15, 1924.

UNITED STATES PATENT lol-Fica enema r. raUNnLn, Jn., or CLEVELAND, omo, assrcNon, BY misma AssIeNunN'rs, To rna'rr a WHITNEY conPnNY, or NEW You, N. Y., a conoiwnoN on Naw JERSEY,

, Application alga July 1,

To all 'whom-t 'may concer/n.:

Be, it known that I, GEORGE T. TRUNDLE, Jr., a citizen of the Unitedl States residing at Cleveland, in the county of uyahoga and State of Ohio, haveinvented a certain new and useful Improvement in Thread- Milling Machines, of which'y the followin is a full,'clear, and exact description, re erence being had to the accompanying drawchine of this character which shall be adapted for the operating, both internally and externally, on parts carried with and rotated by aplurality ofv spindles, mounted in a revolvable head, the milling operation beino effected lby cutters automatically revo ved, the work and cutters being relatively advanced correspondingly to the size and pitch of the thread to be cut. In carrying out this purpose many subordinate objects are incident to the invention, such as the lprovision of' various adjustments and arrangements for replacement of parts, particularly as relates to the manner of holding various work pieces and the thread hobs or cutters.

Further purposes and obj ects of the invention are to so arrange sucha machine that two or more parts may be operated upon simultaneously.l or the operation on such parts may be such that internal and` external milling operations may take place smult'aneously on some of the spindles while others oit the spindles areI automaticallyopened and closed, to facilitate the removalot' the 'finished piece and its replacement'by a fresh piece or part to be operated upon, thus attaining maximum rapidity of operation, greatly increasing the productive capac'ity ot' the machine and reducing to a minimum the amount of time ordinarily wasted inthe operation of such machines.

THREAD-manure IAHINE.

1920. Serial I0. 893,315.

The machine in a preferred embodiment comprises brieiy; a frame carrying suitable driving mechanism including adjustable change speed gearing, for a wide variety of speeds, capable of driving the work spindles and cutters at various relative speeds; a plurality of work spindles mounted in a revoluble head somewhat after the manner of well known types of automatic screw machines; a central driving shaft, a support carrier axially alined with said spindles and adapted to .carry supports adjustable along the same for the work of various lengths; a.

novel mechanism for revolving'the spindle head and for' locking it accurately after each artial revolution, includin means for caus- Ving a revolution correspon ing to space be. tween two or more indles, depending upon the -particular use eing made of the machine; cutter carrying cross slides capable o'f adjustment toward and away from spindle axes,vwith means for automatically moving them longitudinally a material distance, as is necessary foiinternal threading; means for subsequently causing a relative advance of the cutter and work spindles corresponding to the pitch of the thread; and automatic means for feeding the cutter into the depth of the thread and withdrawing the same; automatic and manual means for operating the work holding chucks carried by the cutter spindles; and various accessories, parts and novel characteristics, all of which are hereinafter fully described in connection with the drawings which illustrate my invention.

Subordinate objects. ,and ynovel characteristics will be made more apparent in the following description in connection with the various parts of the mechanism to which they relate', and the essential characteristicsl of the invention are hereinafter summarized in the claims.

In the drawings Fig. 1, is a side elevation of the machine; Fig..2, is a plan view ot the same; Fig. 3, is an end elevation looking toward the left hand end of the machine as represented in Figs. 1 and 2; Fig. 4 is an irregular 4longitudinal vertical cross section showing many of theparts in elevation,

4the plane of the section being represented pproximately by the line 4 4 of Fig. 2; ig. 5 is an enlarged sectional end e evation showing the driving gearing and change speed regulating devices, the planes and operating means therefor, anda slideof the section being .vertical transverse planes approximately on the lines -5 of ig. 2; Fig. 6 vis in the nature of a transverse section through the frame of the machine illustrating the main driving clutch cam mechanism for attaining the required Aadvance corresponding to the pitch of the thread being cut; (Figs. 5 and 6 are made on a scale somewhat enlarged over the scale of Figs. 1 to 4); Fig. i is an enlarged section taken on a vertical plane substantially parallel with the axis of the spindle toward the spindle carrying head and showing the cutter carriers and the mechanism for driving and .advancing them toV and from the work; Fig.v is a similar view in i the nature of a section through the frame of the vmachine taken transversely on a plane indicated by the line 10-'10 of Fig. 2 and also looking toward the spindle carrying head; (Figs. 8 to 11 inclusive are" drawn to approximately the same scale as Fig. 6) Fig. 11 is a vertical section through the mechanism for driving the longitudinal shaftsl and cams, and a mechanism for ad vancing by partial revolutions the spindle carrying head; Fig. 12 is an -enlarged detail view of parts of the advancing mechanism showing them in dierent positions; Fig. 13 is a sectional View of lsuch parts taken Qn an oiset plane indicated by the line 13- 13 of Fig. 12; Fig. 14 is an enlarged detail in plan of the cross slides for advancing the spindle head; Fig. 15 is a section taken substantially on a planeindicated bythe line 15--15 of Fig. 14; Fig. 16 is a detail view showing the cutter in position milling external threads; and Fig. 17 is a similar view showing the cutter acting to mill inf ternal threads. Fig. 18 is a view of the support for long cutters.

In the following description various cliaracters of reference indicate like parts in the several views. v

The frame of the machine comprises essentially a bed portion 1 which is in the nature of a hollow box-like structure form-- plate, carry a transverse support -7 on which is mounted' a two part housing 8 in the nature -of a large circular bearing'for the spindle carrying head. Carried on such up right walls is a longitudinal casting'4 serving as a guide and support for the cutter carriages. At the right hand end of the machine a separate housing 9 forms supports for the longitudinal shafts of the machine and serves to support driving gear mechanism transmitting motion to various parts as will be lhereinafter described. The ed plate and the various supports and housings of the frame are preferably castings arranged to facilitate both the `*foundry and machine work in the manufacture 'of the machine, being divided into various parts, covers and sections in accordance with accepted engineering practice.

For purposes yo tion the general arrangement of drivin shafts and power transmitting elements wi be outlined next. i V f The driving mechanism-Atm is indiclearness in this descripcated a belt pulley mounted onja transverse l shaft 12 journaled at its outer end in an outer bearing carried on a suitable bracket 13. At its. inner end Ithis shaft carries a beveled gear 15', the inner ed of the shaft is supported in separated bearings formed in a housing member 18, provided with a flange bolted to a corresponding flange, formed on an inwardly rojecting bearing member 19, shown as integral with the frame part or housing 3. The bearin 19y supports a shaft 20 on the end of w ich is agear 22 meshin .with, and. driven by a gear 15. The sha t 12 Vis Aintermediately divided, and itsV adjacent ends carry clutch members 24 and 25. The clutch member 25 fits inside of the converging cone sha ed member 27,'removably secured to a mem r 24 by angeson each member which' are bolted together. The member 24 has a boss integral therewith and ke ed to the inner section ot the shaft 12 w ile a spring 28 ics surrounding the shaft bears Iagainst `a shouli der on the member 24, and a thrust bearing 29 carried by the member 25, which is s lined to the outer section of the shaft 12.

i'itside of the hub portionof the member,-

25. is a thrust bearing 30 against which a yoke 311, on a rock shaft 32, may bear to slide the member 25 inwardly against the spring 28 and disengage the cones, allowing the driving pulley to runfreely and permitting the machine` to stop.

To operate the clutch, the yoke 31, which lstradd'lesthe shaft 12, is rocked by means of a lever 33, which may be operated by a lrevoluble cam 34 carried on a rock shaft 35 adapted to be rotated by a hand leVer 36, the cam bears against the inner face` iis lever is swung outwardly to the right (Fig. 6) it moves the lever 33 correspondingly and may hold the lever 1n a position with the clutch disengaged, until the lever is returned manually to its upright position, permitting the springl to cause the engagement of the clutch members. The clutch mayv be opened orA disengaged, also, by means of a link 37 pivoted to the upper endv of the lever 33, and'extending transversely across the machine and pivoted at 38 to a lever 39 similar to the lever 36. 'Thus'the operator may conveniently stop the machine from either side thereof. The shaft 20' carries a series of gears of different sizes rigidly secured thereto and indicated by thel dotted lines 40. gears may in turn bemeshed with movable idler gears, such as 42, carried by swinging and longitudinally iovable levers 44, having a latch handle 45, provided with the usual s ring actuated pins coacting with spaced oles suchi as at 43 in the housing 3. The idler designated 42 is capable of engagement with any of the gears'40. It is shown in Fig. 5 in engagement with the smallest gear. It always meshes with a ear 47. having a fluted engagement with a s aft 50, whereby it may slide along the shaft Aand at lthe same time drive this shaft. The

shaft rigidly carries a gear 54 within the housing 2, (Fig. 4) which meshes with a gear rigid with a shaft 56, extending Vat its lower end, and t longitudinally of the` entire machine an having bearings 57 in the housing 2, and

a bearing 58 in the housing 9. i At the far end of the shaft 56 is a beveled gear 60 meshing with beveled gears 61 on a bearing at rust and radial bearings 66' and 67 .respectively at the top of theiousing 9. v

Near the upper end of the shaft 64 is carried a worm 70 meshing with a worm gear 71, having a fluted driving connection with a shaft 72 supported in a bearing 73 carried in the housing 9, and at its opposite end having a bearing 74 in the spindle carrying head 80. This spindle carryin head comprises in eifach-,a hub portion rigi with large radial 'disk-like members 81 and a vertical shaft 64, having "82, surrounding and rotatable in relation to the shaft 72 and having their peripheries fitted in large bearing surfaces in the housing 8. Projecting forwardly from the spindle carrying head, is an integral tubular member 85 in the nature of a sup-port for centering heads, such as indicated at 86, (Fig. 1).' Within the housing 9 is an inn termittent driving mechanism acting on a gear 87 .rigidly mounted on the end of the support member 85 to revolve the spindle carrying head, as will bel hereinafter more described.

,fulblly ear the lower end of the shaft 64 is a These .cially construetedcam shaft (Fig. 4) comprislng a section carrying a grooved cam 96, and; having abearing at 97 in a wall 98 rising from a bed plate, and an intermevdiate section 99 of special cross sectional contour, formingv a cam' extending longitudinally for a considerable .distance and arranged to operate the cutter carriages at any point of its length, and also having a bearingportion 100in a bearing formed in the wall 6 of the bed plate. Beyond the bear? ing 100 and to the left, (Fig. 4) the shaft extends in a reduced slze again concentric with its own axis and designated 102, and

lhaving a bearing at 103 in the housing member 3, while on this reduced portion'is carried a, Agrooved cam 105 acting through certain mechanism to automatically open and close the chucks of the spindles. Adjacent cam 1.05 is a pair of ,face cams 107 and 109. These cams serve to' operate a lockingdevice hereinafter ldescribed for the spindle head. v

Rising from the housing 2 andv extending .outwardly are housing arms supporting shafts connecting gearing and bearings for driving shafts 110, extending longitudinally one a't each side of the machine and fluted, as shown, to providea sliding engagement for actuating the mechanism driving cutters indicated at 120 (Fi s. 1 arid 2) and shown as operating on' wor indicated at W. The shafts 110 carry on the left hand end bevel gearslll, driven by .bevel gears 112, on` shafts 113 which have suitable bearings in housing arms, as designated 114 and shown as integral with the housing member 2. (Fig. 5.) At the inner ends of the shafts 113 are beveled gears 115,

driven by. gears' 116, on the ends of shafts 117, each of which carries a gear fluted thereto and driven by an idler gear 118,

each in turnv carried by a rocking lever bracket having' positioning hand-operated latches indicated at 119, whereby these gears may be driven .at various speeds, independent'ly of the position of the gearsv 42 driv-A ing the main shaft 50.

The spindles are carried by bearin s positioned in the disks 80 and the spin les as a Whole are designated 125.- They are positioned with their axes parallel with the axis of the spindle head and the shaft 72 whereby they may be driven -in unison and at the same speed by a central gear 75 meshing with the outer gears 76 (Figs. v3, 4 and 7) rigid with each of the spindles.

' slide is moved in the opposite direction by al brief description of the of the machine. l

The longitudinal movement of the spindle head and spindles is accomplished by means of a slide 130 having an upwardly projecting boss 131, in slidable engagement with smooth beveled surfaces on the inner sides of the disks 81 and 82, whereby longitu dinal movement of this slide may correspondingly shift the spindle head. This shifting is accomplished by a slide approximately Vat right angles to the slide 130 (Figs. 6, 7,14 and 1,5) anddesignated 133 and adjustably connected to theA slide 130, to

vary the distance which the spindles may be moved consequent upon thev transverse movement of the slide 133, which is caused by asegmental .gear l134 on shaft 102, engaging al rack 135 on the slide 133. This cam 136 Aacting on a lever 137 connected with the slide. The detailed construction of this mechanism andv its operation will be hereinafter, described.

For' the purpose of. cutting internal threads it i's necessary to move the cutter carriers longitudinallywith relation to the Vs indle head a 'considerable distance, to

t rust the cutter into and out of the work, to cutting position and outwardly away from the 4work. Accordingly. I have shown screwsl 140 `adapted toaccomplish-the ad-v justing'of the longitudinal position of the cutter carrying slides. These screws are rotatably connected with a cross lhead 1112,l

spindle, and centered at theother end by the supports 86,-and that the proper cutters 120 have been selected and positioned in theI cutter carriers the clutch is now rendered activev which results in-the following cycle of operations.' Both of the cutters are fed into the proper cutting depth, whileV the spindles are being rotated through the driving gearing 7 5 and 76, and central shaft 7 2 is in turn rotated by the worm and gear connection with the shaft 64, which is driven by .the shaft 56, rotated at the speed selected at the change gear mechanism.` At the same timemthe entire spindle carrying head, the work and supports 85'with the center supports 86 are moved longitudinally with relation to the cutters, by the slide 130 and its actuating across lslide 133, moved in one direction by the gear 136. The cutters, as stated, areV brought to the proper depth of cut, by the ,long shaft-like cam 99 acting yon *suitable levers, connecting the cam 99 with the carrier slides (as shown in Fig. 9 and to be hereinafter described).

The cutters themselves are' revolved through driving mechanism in the carrier slides, actuated by the luted shafts 110 which are driven at apreviou'sly selected speed through the chan e gear mechanism heretofore described. T is operation continues through more than av` complete revo-v lution of the spindles, thus completing the thread to be cut,whereupon thecutters arey withdrawn from the work and the spindle carrying head is revolved one-half cfa revo- 4 lution, bringing the two opposite spindles to the corresponding cutters, with work previously set up in their chucks and supports. The spindle carrying head is locked 1n this ,newl position and the cam then acts through mechanism to be described to withdraw the spindle chuck lockingl sleeves, allowing the removal of the inis ed work and the positionin 'ofvfresh pieces, which upon the continuv movement of the cam 105 areV 'gripped by the spindle chucks. This takes place'during the cutting on the two opposite spindles. Consequent upon the completion of the cutting operation the cutters are a ain withdrawn and the spindle head revo ved to again bring fresh work to the cutters.

For the purpose of internal vthread milll ing, the' cutters are moved inwardly bringing their spindles approximately to the axes of the corresponding work carrying spindles,-the work is secured in the chucks as before, and the cutters are moved into the interior of the work, that is longitudinally of the cutter spindles, bythe cam 96 actin on the follower' pin 143, and cross head an screws-140 as described, after which the cutl ters are forced into the work during the revolving of the spindles and the relative pitch advance is caused by shifting of the 'spindle head as before. After the complet-4 ing of more than one revolution, making a finished thread, it is necessary to withdraw the cutters by a two-way movement, that is toward the axis of the s indle, out of engavelnent' with the threa s, andthen longitudlnally of the spindle out o the work. These two movements vtake place in succession through the cams 99 and 96.

Various adjustments are provided for 4in the mounting of the cutters and in the methods of holding short pieces of work for internal or external milling, or ,long pieces supported at their free ends by the support 8 5 and center supports 86. The relative advance corresponding to the lpitch of the thread is provided for by adjustment."l The cutting to the correct depth of the ythread is also provided for by mechanism associated with the cutter carriers. When de- Lacasse description is required, except to call attention to the advantages of the general arrangement selected. As will be seen from Figs. v1, 3 and 5, the shafts 117 and their connections to the shafts 110 may be driven at different speeds, but for ordinary purposes of operation where 4the machine is milling the threads on parts of the same character, the shafts 110 are driven. at the same speed in order that -each cutter may rotate at the same speed. It will alsobe apparent that the cutter speed may be varied at will withl relation to the speed of rotation of the cutter spindles and the work, which of course is very much slower. The driving action is transmitted through the gears 42 and 47, (speed being selected by positioning of the gear, 42) through the gears 54'and 55 to the shaft 56, gears 60 and 61 to the shaft 64, and thence through the worm and worm- .gear and 71, sha t 72 and gears 75 and 76, to revolve the spindle somewhat more than one revolution (preferably two revolutions) -while the cutters, of course, make a large number of revolutions, so that the milling of threads may be accomplished smoothly and effectively.

Mechanism for advancing the spindle head corresponding to )Ditch of 'thread-The means for accomplishing the relative advancing of the cutterspindle and work spindles heretofore referred to, is shown particularly in Figs. 4, 6, 7, 8, 14 and 15, and the vparticular arrangement of this mechanism which l have found successful may be described in detail as follows 5 The slide 130 with its boss 131 has arcuate beveled surfaces fitting between corresponding beveled surfaces at the inner edges near the periphery of the spindle carrying disks 81 and 82. This slide is mounted in suitable ways formed above the support 7, shown as cast integral with the vertical supports 5 and 6 of the bed frame, and these ways extend parallel with the axes of the spindle and spindle head. The slide projects outwardly from lthe ways over the slide 133,`

and here carries a downwardly projecting pin 145, secured in place. by a hollow nut threaded into the end of the extension of the slide. The lower end of this pin is closely fitted into acylindrical'opening in aA block 146, ada ted to slide between parallel guideways 14 rigidly supported on a turn-table plate 148, having a circular boss 149 fitting a corresponding cavity formed in tifs the slide 133. Thus this plate may,'s a short ldistance in each direction about the axis of this boss, so that the ways 147 may be set at a slight angle with relation to the ways of the slide 133, (Fig. 14) whereby a longitudinal movement of this slide may effeet .a cam ac tion on the block 146, tra-nsnnttmg a longitudinal movement to the slidel 130 and to the spindle carrying head.

To accomplish the adjustment to vary the movement of the spindle head-I rovide at one end of the turn plate 148, teet engaged lby a screw or worm 150, mounted in a suitable housing and having an angular stud 151 at one end, by which the screw may be turned accurately to change the an le between the guides 147 and the ways or the slide 133. The housing, designated 1,52, for

this worm 150, is shown as secured by suitable screws, one of which extends throughan arcuate slot in the plate 148, which slot permits the swinging movement ofthis plate and at the same time establishes limits therefor.

As previously stated reciprocating movement of the slide 133 is caused by a segmental gear 134 and a cam'136, the ing intermittently on a rack 135 (Fig. 6) for the operating of the slide 133, while the cam 136l is provided with a surface engaged by a roller 154 carried by the lever 137, to 'uickly return the slide. This lever is s own as pivoted at 155 to the slide 133, and also pivoted at its lower end 156 to the framewall 5. As the shaft 102 rotates 4in the direction of the arrow Fig. 6, the teeth of the segmental gear 134 engage the teeth of the rack' 135 and advance the slide 133 accurately at an even speed with relation to the cutting operations which is taking place, moving the slide 133 to thel right, as seen in Fig. 6 and correspondingly moving the spindle head with relation to the cutter to accomplish the proper advance foi-'the pitch of the thread. The spindle headmovement may be in either direction, depending upon whether the thread being cut is right or left hand spiral, and overned by adjusting and swinging slide plate 148. This continues until this advance exceeds the pitch of the thread, that is, through more than a complete revolution of the spindle and work being acted upon by the cutter, and until the gear 134 comes out of,Y engagement with .the rack 135, at-whi'ch time the cam 136 engages the roller 154 and starts the quick return movement, the cutter having been withl`drawn from the work by the cam 99.

gear actzoV `culties occurring b v reason of inaccuracies of alignment of the sections of this cam shaft, such as might occur in the assembling of this machine and the mounting of the housing 9 on the bed plate, which mounting i is preferably adjusted particularly with ref-- erence to the upper shaft 72 and carrier 85.

vThe relationshipof the teeth and pitch of the worms and worm gears 70 and 71, and 90 and 91 is such that the shaft 72 has two revolutions to one revolution of the v'cam 99, and it 'may be stated at this pointthat the central gear 75 being slightly larger thanits surrounding gear 76, causes somewhat more/than two complete revolutions of each of the spindles to one revolution of theA cam 99. This vprovides for the cutter being fed into the work, to its proper depth and maintaining that depth while cutting the thread, for more than a complete revolution, and then withdrawing from the completed thread so that the cutter is freed during the subsequent longitudinal movement of the work. This movement is the quick return caused by the cross slides actuated by the cam 136, moving with the cam 99. It will be seenthat these movements occur in the following order; indexing of the spindle head, inoving the cutter into the work-as the spindleA is revolved, maintaining the cutter in .this position for more than a-,complete revolution, drawing the cutter out of the work as the spindle continues to revolve, and maintaining it in its withdrawn position while the spindles are moved longitudinally and again indexed or revolved to present fresh work to the cutters, which are vthereuponjmoved inwardly as before.

bearings for the cutter spindle designated 165, on which is carried a spiral gear 166, driven by a spiral gear 167, rigid on shafts 168. This shaft has bearings in the housing 164 and extends outwardly from said housing through bearings carried in a cylindrical housing member 169, shown as integral with sup rting arms or brackets, rising fromand integral with the longitudinal 'shaft and transmit motion to the gears 170,

slides 160. Between 'the bearin 'in the housing 169 I have-shown a spira gear 170 meshing with a spiral gear 171l` having! teeth engaging the flutes of the shaft 110, whereby the gears 171 may slide along the' which,'in turn, have fluted engagement with the shaft 168, allowing a relative movement with its shaft 170, and at the same time transmitting motion through its gear 166 and 167 to the cutter indles.`

At 173 is shown a cy indrical support carried in the housing 164 and on which may be mounted center or bearing supports (Fig. 18) for en ging the outer ends of the cutters when t is may be desirable. y, f The housings 164 aresldably mounted in suitable ways, parallel with the ways engaged by the slides 163r and formed on theupper side of each slide'163, whereby the 85 cutter spindles may be adjusted radially with relation to the axis of the spindle head. The iiuted engagement .of the shaft 168 and gear 170 provide for driving the cutter regardless of its position within the limits of its movement. To provide for this cutterv adjustment which must'be very accurate I have shown l an outwardly extending member, rigid with" the cutter spindle housing 164 and carrying 95 a nut at.17 2, engaged by a screw extending outwardly through a bearing 174 rigid with the plate 163, and having an angular extension at 175 by which the screw may be-conveniently rotated. Mounted on tne extension of the screw is shown a cap 176 which may be graduated on the exterior to-fa'cilitate accurate adjustment of the position of the cutter. I

The parts of the cutter carriage and driving mechanism therefor are all arranged so as t0 be closed and protected by the housings and their cap members, which in several instances form portions ofthe bearings as is a parent from the drawings (Figs.`9 110 and 10 To protect the outwardly extending ends of the shaftsl 168 they may be inclosed by a tubularhood indicated as at 177. Extending downwardly and ,inwardly from each slide plate 160 is a bracket arm 1'1'5 Y 180, carrying at its lower end a pivot pin 181 for a lever which serves to feed the cutters by moving the cutter carriages toward and away from the work. -These levers are shown as comprising integral arms 182 120 and 183 extending each way from a hub, embracing the pivot pins. rl.`he arms 182 may be bifurcated at their upper ends to receive square blocks eac-h embracing a pin indicated at 184, the ends of which pin engage suitable ears rigid with the plate 163. y The inner ends of the lever arms 183are bifurcated to embrace the shaft-like cam 99. Each arm carries rollers'indicated at 186 embracing opposite sides, that. is, the upper m and lower side, of this cam whereby the rotation of this cam may rock the levers and move the slides '163 with the cutters toward and away from the Work. The surfaces of the cam 99, as stated, are uniform in their longitudinal extent, whereby as the slides 160 are moved along the longitudinal ways, parallel with the axis of the shaft, and with the axis of thespindle head, the lever movement may takev place at any such position given the cutter carriages. The surfaces are so arranged in contour that with the rollers and levers arranged as shown the cuttersv may first be moved toand into engagement with the work and then by rest surfaces, that is, concentric surfaces, may be held in this position accurately during more than a complete revolution of the spindles, while the work is being operated upon, and then another surface of the -cam acting upon the rollers may cause the levers to move the rollers simultaneously outwardly lfrom the work after the cutting of the threads-is finished. y

The moving of the cutter carriages along the guide ways 162 to bring the cutters accurately to any desired positionv corresponding to the Work to be operated upon, is accurately effected by means' of the screws 140, which extend through downwardly projecting bosses 188, threaded tol receive these screws, as is apparent in Fig. 9. The rotation of screws is rendered convenient by the angular portions 189 at the outer vside of the cross head 142. This cross head 142 is shown,

as carried on a slide 190 (Figs. 4, 9 and 10), the ways for the slide being formed in the frame member 4 which is shown as integral with the guide ways 162. The purpose of the slide 190 is to support the cross headl 142 rigidly against the various .strains brought to bear thereon .by reason of the lengagement; ofthe pin 143, carried thereby,

the cutter, that is the cutter carriages may be moved quickly away from Ithe, work `and returned, and during the remaining portion of the cycleof the cam may be held accurately in one position while the cutting of the threads is taking place.

Mechanism for intermittently revolving the spindle head-T he cam 95 on the shaft 92, whichdrives the cam shaft governing p `the spindle head. a comparatively quick outward movement of A the motion of the cutter spindles as just described, may govern the mechanism for revolving the spindle head through mechanism, shown particularly in Figs. 4, 11, 12, and 13. On the end of the tubular 'sup ort 85, which as stated is integral with the isks and 81 forming the spindle carrying head, the gear 87 is rigidly mounted, and is adapted to be driven by a gear 192'meshing therewith and preferably twice the size of the gear 86. The gear 192 is mounted on a shaft 194, having bearings in the walls of the housing 9, and splined to this shaft is a lclutch member 195 embraced by a yoke, pervalso having an arm carrying a roller 198 engaging the cam slot of the cam 95. Secured to the outer face of the worm gear 71 is a disk-like member 200, having a crank pin 201, embraced by the end of a connecting rod 203, the other end of which embraces a pin, at 204, in turn carried by a rock arm 205 integral with a suitable hub keyed to the shaft 194.

The arrangement of the crank pin 201, connecting rod 203 and rock arm .205 is such that as the worm gear 71 rotates, the rock arm 205 and' shaft 194 are continuously oscillated. With theparts in the postion shown inlFig. 11 the oscillation of the shaft 194 and its rock arm is through an' arc of 900, which transmits a motion whereby clutch teeth on the side of the clutch member 195 may engage clutch teeth 193. on the side of the gear 192, in one position, and cause a corresponding rota-l Vis again locked. During the period of operation of the cutters the cam holds the clutch member 195 free from the clutch teeth 193 throughout a complete revolution. and causes this engagement on a part of a second revolution for again advancing The connecting rod 203 is provided with an additional opening 207 adapted to be brmght into registration with`a corresponding .opening 208 in the disk 200 so that the pin .201 may be removed and placed in these openings. thus causing the pin to revolve in a ,circle of one half the diameter' of that of its previous path. This causes the oscillation of the shaft 194. through the rock arm 205, thus oscillating the clutch 

